In "Who's That Girl?," Madonna plays the sweet and playful parolee Nikki Finn. After serving time for a murder she didn't commit, she gets out of jail and enlists the engaged Loudon (Griffin Dunne) to help her clear her name. Between their various misadventures (losing a rare tiger, stealing at the mall, gun play at a seedy gun shop with a psycho owner), Loudon realizes that his superficial fiance Wendy is not for him. Then, during his own wedding to Wendy, he decides to be with Nikki. Then chaos ensues as the hitmen who have following Nikki arrive and want to kill her.

The movie has not held up well over the years. However, Madonna's theme "Who's That Girl?" has. Written by Patrick Leonard (Jewel's "Spirit" album) and Madonna, the single opens with the now classic and Latin-inspired drum beat. In the first verse, she stays true to the romance in the movie, by talking about her character's charms ("when you see her, say a prayer and kiss your heart goodbye" & "her laughter burns up inside")

In the chorus, she sings in Spainsh, questions asking "who's that girl" (assumedly) while adding "who's that girl" at the end. The Spainsh lyrics are an nice touch, although it does not make any sense to be in the song whatsoever.

In the second verse, she focuses on Griffin Dunne's character, Loudon and his attraction to her ("you try to avoid her/fate in is your hands...now you're falling at her feet/you try to get away but you can't.") The bridge, though, is the best part of the single. It begins, with Madonna singing in her lower register, "light up my life/so blind I can't see/light up my life/no can help me now" There's a brief dance break, with only drums and keyboards. The second time it's sung (1:09), Madonna adds "who's that girl" underneath the arrangement. She's breathy and mischievous, while singing "Now/who's that girl." It's starts soft, then she hits the crescendo the third time and it's like a celebration once the chorus kicks in again.

More dance than pop, the single stays away from typical 80s music cliches ( the saxophone, notably) which is why 15 years later, "Who's That Girl" sounds as fresh as it did in 1987.